1. Field of Invention
This invention pertains to a flashlight with soft turn on control, and more particularly to a flashlight with circuit for limiting the surge or inrush current through an incandescent bulb thereof.
2. Description of the Prior Art
Typically, a flashlight has to be relatively small so that it can be hand-held and to minimize its storage space. Therefore the controls for the flashlight are made as simple as possible. Thus, a standard flashlight with a single incandescent bulb is normally provided with only a mechanical on/off switch for feeding current to the bulb from a power source such as one or more batteries. The bulb, switch and batteries are normally enclosed in a common housing. One problem which this arrangement is that the initial or surge current to the bulb is substantial. This large surge current (sometimes termed inrush current) seriously degrades the bulb because it imposes a large thermal and mechanical strain on its incandescent filament and switch contacts. This strain reduces the useful life of the bulb and often leads to its premature failure. For example, a bulb used in a flashlight which is activated frequently has a much shorter life than a bulb used in a flashlight which is activated only rarely even if the second flashlight is on for a longer time than the first flashlight. This problem is aggravated even further if the flashlight is provided with an activating switch with bounce, i.e. a switch which closes and opens several times in quick succession every time the switch is turned on. Thus a single activation of the switch causes several sequential current surges through the fillament in a relatively short time period.